The following information is provided to assist the reader in understanding technologies disclosed below and the environment in which such technologies may typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the technologies or the background thereof. The disclosure of all references cited herein are incorporated by reference.
Prudence dictates that gas detection instrumentation be tested regularly for functionality. It is a common practice to, for example, perform a “bump check,” or functionality check on portable gas detection instrumentation on a daily basis. The purpose of this test is to ensure the functionality of the entire gas detection system, commonly referred to as an instrument. A periodic bump check or functionality check may also be performed on a permanent gas detection instrument to, for example, extend the period between full calibrations. Gas detection systems include at least one gas sensor, electronic circuitry and a power supply to drive the sensor, interpret its response and display its response to the user. The systems further include a housing to enclose and protect such components. A bump check typically includes: a) applying a gas of interest (usually the target gas or analyte gas the instrument is intended to detect); b) collecting and interpreting the sensor response; and c) indicating to the end user the functional state of the system (that is, whether or not the instrument is properly functioning).
Such bump tests are performed regularly and, typically, daily. Bump checks provide a relatively high degree of assurance to the user that the gas detection device is working properly. The bump check exercises all the necessary functionalities of all parts of the gas detection device in the same manner necessary to detect an alarm level of a hazardous gas. In that regard, the bump check ensures that there is efficient gas delivery from the outside of the instrument, through any transport paths (including, for example, any protection and/or diffusion membranes) to contact the active sensor components. The bump check also ensures that the detection aspect of the sensor itself is working properly and that the sensor provides the proper response function or signal. The bump check further ensures that the sensor is properly connected to its associated power supply and electronic circuitry and that the sensor signal is being interpreted properly. Moreover, the bump check ensures that the indicator(s) or user interface(s) (for example, a display and/or an annunciation functionality) of the gas detection instrument is/are functioning as intended.
However, a periodic/daily bump check requirement has a number of significant drawbacks. For example, such bump checks are time consuming, especially in facilities such as industrial facilities that include many gas detection systems or instruments. The bump check also requires the use of expensive and potentially hazardous calibration gases. Further, the bump check also requires a specialized gas delivery system, usually including a pressurized gas bottle, a pressure reducing regulator, and tubing and adapters to correctly supply the calibration gas to the instrument. The requirement of a specialized gas delivery system often means that the opportunity to bump check a personal gas detection device is limited in place and time by the availability of the gas delivery equipment.
Recently, a number of systems and methods have been proposed to reduce the number of bump tests required. Such a system may, for example, include electronic interrogation of a sensor. A sensor is offline or unable to sense an anlayte or target gas or gases during such electronic interrogation. For example, a number of sensors include functionality to electronically interrogate of one or more electrodes thereof, require a user to initiate an interrogation process which takes between 20-30 seconds. For example, a potential change may be applied to an electrode for 5-10 seconds and the corresponding current decay curve is studied over a 20-30 second period. As set forth above, during such a 20-30 second period, the sensor is offline and can't be used to sense the analyte(s). It is desirable to minimize the amount of time a sensor is offline, particularly in cases wherein a sensor is used to detect one or more hazardous analytes or target gases.